1. Field of the Invention
This invention is in the field of cardiology and methods therefor and, more particularly, is a system and method for detecting and locating heart disease, and especially coronary artery disease including myocardial ischaemia and infarction; however, the act of locating is with reference to myocardial ischemia and infarction.
2. Description of the Related Art
Coronary artery disease is the leading cause of death in the United States, yet the disease remains xe2x80x9csilentxe2x80x9d or dormant in the majority of patients until the fourth or fifth decade of life. At that point, coronary artery disease typically moves from the xe2x80x9csilentxe2x80x9d phase to a symptomatic phase, at which time the patient may experience as the first symptoms, angina pectoris, myocardial infarction, and/or sudden death.
The prevalence of coronary artery disease in the United States has been estimated as affecting over 4 million persons. Over 1 million are expected to suffer myocardial infarctions or sudden death before attaining the age of 60. Furthermore, once coronary artery disease is symptomaticxe2x80x94regardless of whether the symptoms comprise angina or myocardial infarctionxe2x80x94the mortality rate is increased to 4% per year overall and 8% per year in those patients with an abnormal electrocardiogram or hypertension. This increased mortality rate is largely due to increases in the occurrence of sudden death, or the complications of repeated myocardial infarction.
Prior approaches to diagnose coronary artery disease fall into four general categories, which will be briefly discussed below. The first category falls under noninvasive, conventional EKG type tests, like the standard 12 lead EKG. Also, in this first category, some have practiced 24 hour ambulatory monitoring of the conventional EKG and stress test (see U.S. Pat. No. 3,267,934 to Thornton). This category of tests give ST segment depression and elevation readings as an indicator of myocardial ischaemia. However, ST segment changes are only sensitive to some portion of coronary artery diseases. Accordingly, tests such as these have limited value for the diagnosis of coronary artery disease, as they are relatively insensitive in detection of certain potential events. A second group of approaches to detect coronary artery disease involves more expensive noninvasive tests, such as nuclear imaging. Also, this cluster in of approaches may involve an invasive assessment of cardiac catheterization and coronary angiography. This second group of tests has the disadvantage of being expensive and/or invasive.
A third approach to the detection of coronary artery disease involves the use of software programs to analyze conventional EKGs. One such approach is the cardiointegram (CIG) which applies a process of integration over various sections of the QRST signal. The High Frequency Electrocardiogram (HFECG) is another software-based method which derives high frequency components of the EKG following a fast-Fourier transformation. The methods of this third group of approaches are either performed on every single heart beat or on the averaged QRS complex. When analyzing single heart beats, much potentially meaningful information is simply not evaluated. On the other hand, techniques based on analyzing a single averaged QRS complex seem to be able to distinguish minor signal changes from noise, but there are significant limitations to these types of methods as well. For example, the averaged EKG is based on the QRS superimposition, and the precision of superimposition is limited by sample rate, QRS identification software, analytical experience of the user, and heart rate variability. Accordingly, use of this third group of analysis techniques is also limited in terms of effectiveness at fully and accurately detecting coronary artery disease.
A fourth technique is exemplified by an article entitled xe2x80x9cThe Theoretical Basis and Clinical Study of EKG Multiphase Information (EMP1) Systemxe2x80x9d (for The American Society of Hypertension, Sixth Scientific Meeting by Dan Qun Fang et al.), and by U.S. Pat. No. 5,509,425, entitled xe2x80x9cArrangement for and Method of Diagnosing and Warning of a Heart Attack.xe2x80x9d In this a approach, power spectrum and other frequency domain analyses are used to extract additional information from a conventional EKG; however, this technique also has its shortcomings. Specifically, Fourier transformation of the time domain signals into the frequency domain is conducted on only two EKG leads, namely lead V5 and lead II, thereby unnecessarily forfeiting the very potentially beneficial analyses of the remaining EKG leads. Additionally, this approach failed to establish use of a base value (as set forth in the current invention) in its analysis of power spectrum signals.
Therefore, there existed a need to provide a system and method for improved detection of coronary artery and heart disease. Moreover, the instant invention provides a system and method for not only detecting coronary artery and heart disease, but also locating such ailments, when detected.
An object of the present invention is to provide an improved system for detecting coronary artery and heart disease and a method therefor.
Another object of the present invention is to provide a system for locating the source or sources of detected coronary artery and heart disease and a method therefor.
Yet another object of the present invention is to provide a system for detecting and locating the source or sources of coronary artery and heart disease by analyzing at least one, and preferably all, of 12 lead signals transformed into power spectrum signals in the frequency domain.
Still another object of the present invention is to provide a system for detecting and locating the source or sources of coronary artery and heart disease by using a base value, derived from a patient""s heart rate, in analyzing at least one, and preferably all, of 12 lead signals transformed into power spectrum signals in the frequency domain.
According to one embodiment of the present invention, a method for detecting and locating heart disease is disclosed comprising the steps of obtaining electrocardiograph (EKG) signals from a patient, modifying the EKG signals, and establishing a base value for use in evaluating modified EKG signals. The step of obtaining includes the steps of providing an electrocardiograph, providing a plurality of connectors between a plurality of locations on the patient and the electrocardiograph, and operating the electrocardiograph to take readings from the plurality of locations and to output the EKG signals. Note that the plurality of locations include positions proximate the patient""s Right Arm (RA), Left Arm (LA), Right Foot (RF), Left Foot (LF), and six separate areas on the patient""s Chest (C1-C6).
The step of modifying includes the steps of mathematically modifying the EKG signals to obtain altered signals in the time domain, and converting the altered signals in the time domain into power spectrum signals in the frequency domain. Additionally, note that the step of modifying further includes the steps of amplifying the EKG signals, and digitizing amplified EKG signals. The altered signals in the time domain comprise at least one of 12 lead signals, namely, lead I, lead II, lead III, lead aVR, lead aVL, lead aVF, lead V1, lead V2, lead V3, lead V4, lead V5, and lead V6.
The step of establishing the base value comprises the steps of obtaining the patient""s heart rate, and applying a conversion factor to the heart rate to obtain the base value. The step of obtaining the patient""s heart rate comprises at least one of measuring the patient""s heart rate, and acquiring the patient""s heart rate from data relating to physical and medical characteristics of the patient. Preferably, one""s heart rate comprises the patient""s resting heart rate. The step of applying the conversion factor comprises the steps of converting the heart rate defined in beats per minute to beats per second, and multiplying the heart rate defined in beats per second by a scaling quantity. The scaling quantity comprises any number between approximately three and seven, inclusively, however, note that the scaling quantity preferably comprises the number five.
The present method further comprises the steps of calculating a first area by integrating a selected one of the power spectrum signals from zero Hertz to the base value, calculating a second area by integrating the selected one of the power spectrum signals from the base value to infinity, and dividing a first calculated value corresponding to the first area by a second calculated value corresponding to the second area to obtain al evaluation standard corresponding to the selected one of the power spectrum signals. A first state of the evaluation standard comprises a value of approximatelyxe2x89xa7one to indicate a healthy state for the patient, and a second state of the evaluation standard comprises a value of approximately less than one to indicate an unhealthy state for the patient. The present method further includes the step of obtaining a separate evaluation standard for each of the power spectrum signals in the frequency domain.
Additionally, the present method comprises the step of analyzing peaks for each of the power spectrum signals in the frequency domain against a plurality of evaluative standards for the peaks. The evaluative standards for the peaks include at least one, and preferably all, of determining if a second peak is greater in magnitude than a first peak for any of the power spectrum signals as indicative of an unhealthy state for the patient, determining if a fifth peak is greater in magnitude than the first peak for any of the power spectrum signals as indicative of an unhealthy state for the patient, determining if the fifth peak is greater in magnitude than a third peak for any of the power spectrum signals as indicative of an unhealthy state for the patient, determining if a fourth peak is greater in magnitude than the third peak for any of the power spectrum signals as indicative of an unhealthy state for the patient, determining if the first peak is relatively low in magnitude for any of the power spectrum signals as indicative of an unhealthy state for the patient, determining if the third peak is relatively low in magnitude for any of the power spectrum signals as indicative of an unhealthy state for the patient, determining if the first, second, third, and fourth peaks are relatively low in magnitude for any of the power in spectrum signals as indicative of an unhealthy state for the patient, and determining if the first, second, third, and fourth peaks are relatively high in magnitude for any of the power spectrum signals as indicative of an unhealthy state for the patient. Note that the aforementioned first, second, third, fourth, and fifth peaks correspond to the first five consecutive peaks in any of the power spectrum signals as viewed moving up in frequency from zero Hertz in the frequency domain.
The methodology for locating the heart disease comprises the steps of providing a plurality of locating standards wherein each locating standard corresponds to a distinct location of potential heart disease, and evaluating each locating standard of the plurality of locating standards to determine whether any distinct locations have heart disease. The step of providing a plurality of locating standards comprises the step of establishing a sum of different evaluation standards for each locating standard of the plurality of locating standards. Moreover, the step of evaluating each locating standard comprises the steps, repeated for each locating standard, of adding the sum of different evaluation standards for the selected locating standard, comparing the sum to the number of evaluation standards comprising the sum for the selected locating standard to determine whether the sum isxe2x89xa7the number of evaluation standards, and to determine whether the sum is less than the number of evaluation standards, assigning the distinct location of the potential heart disease corresponding to the selected locating standard with a determination of an unhealthy state for the patient when the sum is less than the number of evaluation standards, and assigning the distinct location of the potential heart disease corresponding to the selected locating standard with a determination of a healthy state for the patient when the sum isxe2x89xa7the number of evaluation standards. The plurality of locating standards and their corresponding distinct locations of potential heart disease define an analysis table comprising: (1) V1+V2+V3+V4⇄Anteroseptal, (2) V2+V3+V4+V5⇄Anterior, (3) II aVF+V1+V2⇄Inferior Posterior, (4) I+aVL+V3+V4+V5+V6⇄Anterolateral, (5) I+aVL+V5+V6⇄Lateral, (6) I+aVR+aVL+V6¦Lead I Area, (7) II+aVR+aVF⇄Lead II Area, (8) III+aVL+aVF⇄Lead III Area, (9) I+II+aVR+V5⇄Lead aVR Area, (10) I+III+aVL⇄Lead aVL Area, (11) II+III+aVR⇄Lead aVF Area, (12) V1+V2+V6⇄Lead V1 Area, (13) V1+V2+V3⇄Lead V2 Area, (14) V2+V3+V4⇄Lead V3 Area, (15) V3+V4+V5⇄Lead V4 Area, (16) V4+V5+V6⇄Lead V5 Area, (17) V1+V5+V6⇄Lead V6 Area, (18) V1+V2⇄Septal, and (19) II+aVF⇄Inferior. Note that the corresponding distinct locations of potential heart disease identified above are well known to those skilled in the art.
Note that when the sum isxe2x89xa7its corresponding number of evaluation standards for each locating standard of the plurality of locating standards, no distinct location of potential heart disease is detected. When the sum is less than its corresponding number of evaluation standards for only one locating standard of the plurality of locating standards, the distinct location corresponding to that one locating standard has detected heart disease. When the sum is less than its corresponding number of evaluation standards for more than one locating standard of the plurality of locating standards, each distinct location corresponding to those xe2x80x9cmore than one locating standardxe2x80x9d of the plurality of locating standards has detected heart disease. When a plurality of locating standards have their sums less than their corresponding number of evaluation standards, the most accurate prediction of the distinct location for the detected heart disease corresponds to the locating standard of the plurality of locating standards with their sums less than their corresponding number of evaluation standards that is located highest on the analysis table. Then, the remaining locating standards of the plurality of locating standards having their sums less than their corresponding number of evaluation standards are of lesser accuracy in completely locating the area of detected heart disease as their corresponding distinct locations move down the analysis table. In other words, a for the plurality of locating standards with their sums less than their corresponding number of evaluation standards, the corresponding distinct locations of detected heart disease are listed from most to least accurate in fully and completely locating the heart disease, from the top to the bottom of the analysis table.
Note that in the present invention, at least one but less than all of the plurality of locating standards may be evaluated to determine whether any of the distinct locations have heart disease. Alternatively, all of the plurality of locating standards may be evaluated to determine whether any of the distinct locations have heart disease. In the preferred embodiment of the present invention, all of the 12 lead signals are simultaneously and continuously obtained over a period of time for the step of converting the altered signals in the time domain into the power spectrum signals in the frequency domain; however, less than all of the 12 lead signals may be procured as noted. Generally, the period of time comprises a duration in excess of one second; however, the period of time preferably comprises a duration of approximately 88 seconds.
According to another embodiment of the present invention, a system for detecting and locating heart disease is disclosed comprising, in combination, means for obtaining electrocardiograph (EKG) signals from a patient, means for modifying the EKG signals coupled to the means for obtaining, and means for establishing a base value for use in evaluating modified EKG signals. The means for modifying further includes means for amplifying the EKG signals, means for digitizing amplified EKG signals, and a processor coupled to the means for digitizing. The processor includes means for mathematically modifying the EKG signals to obtain altered As signals in the time domain, and means for converting the altered signals in the time domain into power spectrum signals in the frequency domain. Note that the altered signals in the time domain comprise at least one of 12 lead signals, namely, lead I, lead II, lead III, lead aVR, lead aVL, lead aVF, lead V1, lead V2, lead V3, lead V4, lead V5, and lead V6.
The means for establishing a base value comprises means for obtaining the patient""s heart rate, and means for applying a conversion factor to the heart rate to obtain the base value. The means for applying the conversion factor comprises means for converting the heart rate defined in beats per minute to beats per second, and means for multiplying the heart rate defined in beats per second by a scaling quantity. The scaling quantity comprises any number between approximately three and seven, inclusively, however, the scaling quantity preferably comprises the number five.
The processor further includes means for calculating a first area by integrating a selected one of the power spectrum signals from zero Hertz to the base value, means for calculating a second area by integrating the selected one of the power spectrum signals from the base value to infinity, and means for dividing a first calculated value corresponding to the first area by a second calculated value corresponding to the second area to obtain an evaluation standard corresponding to the selected one of the power spectrum signals. A first state of the evaluation standard comprises a value of approximatelyxe2x89xa7one to indicate a healthy state for the patient, and a second state of the evaluation standard comprises a value of approximately less than one to indicate an unhealthy state for the patient.